Voltage control system



A. N. ANDERSON 1,817,334

VOLTAGE CONTROL SYSTEM Filed Sept. 2- 1927 Patented Aug. 4, 1931 UNITED STATES PATENT. DFFICE GE 993E59 fiYSTEM Application filed September This invention relates to a system and apparatus for supplying a constant voltage output from a variable. current source.

The invention is more particularly applicable for supplying a constant low voltage current from a variable high current source, and is especially useful in supplying electric scales,or other devices requiring a substantially constant low voltage current, 15) with the necessary low oltage on which they operate from the usual 1-1()--v olt current supply line.

. It is recognized that there is considerable voltage variation in commercial 'l10-volt 15 lines, and that when this current is stepped down through a transformer for use with electric scales, that the operation of the scales varies according to the current Varia: tions in the supply lines. This is, of course, 20 detrimental to the accuracy of the scales.

The present invention may be readily understood by reference to the accompanying drawing, which illustrates diagrammatically a system and apparatus for supz; plying a constant lower voltage from a higher voltage source.

In accordance with the present invention, there is provided a balance beam 1 mounted on a fulcrum 2 and having a coil 3 at one end thereof. This beam may be of the type commonly employed in certain electrical measuring instruments, such for instance as the well-l nown Kelvin balance. The coil is connected in series and disposed between upper and lower coils 4 and 5, respectively. The coils 4, 3 and 5 are connected in series, through wires 6 and 7 shunted across wires 6 and 7 which lead to the scales or other device to which the constant voltage current is applied. \Vires 6 and 7 are in the secondary circuit 8 of a transformer 9 having a primary winding 10. One side of the primary 10 is directly connected with one side of the 110-volt line L through wire 11. The other side of the primary connects through a variable resistance 12, and a movable contact 13 with the other side L of the line.

At the end of the beam 1 is a contact making element 14 which may move into contact with either an upper contact mem- 2, 1927. Serial No. 217,284.

her 15 or a lower contact member 16, depending on which direction the beam 1 is rocked. Contact member 15 is in circuit with solenoid 17, which 'is connected through wire 17" with one side, "L, of the supply current. Contact member 16 is in circuit with solenoid 18 and the side L of the 11(l-volt line. The other side, L, of the llO-volt line is connected with the contact member 14 on the beam 1 through a suitably arranged wire 19.

On the free end of thevbeam 1 is .a counterweight which is preferably .in the form of a flexible cord orstring 20 having a series of beads 21 arranged thcrealong. The heads 21 are preferably non-magnetic and are preferably of a moisture-resisting material, such for instance as glass. One end of this flexible colmter-weight is directly connected on the end of, the balance beam, .whilelthe other end of the flexible counter-weight 19 is wound over a spoolQor drum 22. The drum 22 can :be adjusted manually to vary theefiective length ,of the counter-weight 20 21, according .to the conditions ,of the circuit and the output desired in the wires 6 and 7.

The solenoids 1 7 and 18 are provided with armatures which areconnectcd with a pivot ed beam 13*, this "beam being pivoted at '18,. Q3 of the armatures-is located .one side of the pivot point, and one of the armatures the other side of .the pivot point, and the morable'c nta t :13 is car ied on the free 1d a thiss sond hem- 11 th op ra on 9f th ystem, assum ha th n f v i uppose to d l ter a cement Q tou o t o t ie ;-6 and 7- The adjustable vweight is set hold coil 3 and was b am 1 the n ut al nes tio n sh own in the drawings when the normal voltage is flowing through the a 7- the e isa rariatiq in $1.1 i p g ip la wnsnayb aa Striated 9N01 v r ii new "l n th s varia t ion will 'be instantly reflected in the lines 6 and 7. Any di sturbance in the curren-t value in lines 6 and 7 will l causethe armature -3 to be moved up and'dowm thereby bringing contact member 14 inwarcua closing position with either contact 15 or contact 16, depending on the fluctuation of the current, thereby energizing either coil 17 or 18, as the case may be. Energization of either of the solenoids 17 or 18 will effect a movement of the beam 13 to vary the resistance 12 in the circuit of the primary winding 10 of the transformer 9.

As thus arranged, it will be seen that if there is a voltage drop in the llO-volt lines, the contact member 13 will move down, cut ting out resistance in the primary circuit but if there is an increase in the supply of voltage, the lever 13 will move in the opposite direction to cut in more resistance in the primary circuit. This will tend toward maintaining a constant output voltage across lines 6 and 7.

In place of the particular flexible counter weight illustrated, any suitable counter-act ing mechanism may be substituted, but a mechanism is preferably used which can be variable so that it can be readily set according to particular conditions of use, and a flexible weight such as that shown is preferred because of the fine increments of adjustment obtainable, together with the constant effect which is exerted thereby, as compared with the variable nature of the springs and similar counter-balancing devices, such as are sometimes employed.

The advantages of the present invention arise out of the fact that a simple arrangement is provided for effectively maintaining a substantially constant potential across the lines 6 and 7, whereby a current supplied from commercial lines can be effectively utilized in connection with electric weighing scales or other electrical apparatus requiring a substantially constant current for their operation.

\Vhile the apparatus disclosed is relatively simple, it is extremely responsive to small current variations, utilizing as it does, principles of the Kelvin balance, and delicate increments of adjustment can be readily obtained.

While I have diagrammatically illustrated one system embodying the invention, it will be understood that the form illustrated is merely illustrative of one embodi ment, and that the invention may be otherwise embodied, and that various modifications and changes may be made within the spirit of my invention and under the scope of the following claims.

I claim:

1. A voltage regulating system including input and output circuits, a Kelvin balance in the output circuit, a iheostat in the input circuit, and means responsive to a movement of the balance for varying the rheostat, said balance having a beam, a flexible counterbalance for the beam, and means for adjustably varying the flexible counten balance.

2. A voltage regulating system including input and output circuit-s, a Kelvin balance in the output circuit, a rheostat in the input circuit, means responsive to a movement of the balance for varying the rheostat, said balance having a beam with a flexible cord attached thereto, beads on the cord to provide a counterbalance for the beam, and means for increasing or decreas ing the effective length of the counterbalance.

3. An alternating current source of variable voltage, electric scales requiring a constant voltage low in magnitude as compared with the voltage of said source, means whereby a constant low voltage may be supplied to said scales by said alternating current source, including a step-down voltage transformer having its high voltage primary winding energized by said source and its secondary low voltage winding energizing said scales, a variable resistor in series circuit with the high voltage winding, a Kelvin balance across the low voltage winding, and means energized by said balance for uniformly changing the resistance of the resistor in accordance with changes in the voltage of the low voltage winding, whereby a constant low voltage is supplied to the scales.

In testimony whereof I have hereunto set my hand.

ARTHUR N. ANDERSON. 

